Australia has transferred the first group of asylum seekers to a processing centre in Papua New Guinea, immigration officials say.

A flight carrying 19 asylum seekers from Sri Lanka and Iran arrived in PNG early on Wednesday.

They will be the first detainees at the newly-reopened camp on Manus Island.

Australia has also recently reopened an offshore processing centre on Nauru, as it puts back in place a controversial policy it ended four years ago.

The government decided to re-establish offshore processing camps in August, after ending the policy - known as the Pacific Solution - in 2008.

The move, recommended by an expert panel, came in response to a sharp rise in the number of asylum seekers arriving by boat.

The government says offshore processing is aimed at deterring people from making the dangerous journey across the sea to Australia.

Several boats have sunk or had to be rescued in recent months as they sailed from Indonesia to the Australian territory of Christmas Island.

But critics say the policy is inhumane and provides inadequate protection for the human and legal rights of asylum seekers held offshore.

Rights probe

Australia closed its camp on Manus Island eight years ago, but soldiers have been working to re-open it in recent weeks.

As on the tiny Pacific territory of Nauru, detainees will have to live in tents until more permanent structures are built.

Police, immigration officials and interpreters accompanied the group on the flight from Christmas Island to Manus Island, a statement said.

On Tuesday, representatives of rights group Amnesty International visited the asylum camp on Nauru to assess conditions, after reports of hunger strikes and self-harm incidents.

Their formal report is due later this week, but in comments to Australian broadcaster ABC a representative highlighted concern over overcrowding, damp, hot tents and detainees' fears over the time it will take to process their claims.

Since the camp in Nauru was reopened in early September, more than 370 asylum seekers - mostly from Sri Lanka and Afghanistan - have been transferred there.

In recent weeks both the ruling Labor Party and the opposition have suggested that asylum seekers could have to spend as long as five years in camps while their claims are processed.

Overnight, meanwhile, two boats carrying a total of 137 asylum seekers were intercepted by Australian naval and border vessels, the government said.